Quadtree in C/OpenGL help?

[Seraphim0240]

I'm having trouble with my deleteNode function... I need the program to be able to delete only one node when you right click on it, but not the rest of the nodes in the quadtree.

Here's the current deleteNode function... let me know if you see the problem or the logic that I am missing!

void deleteNode(qnode *root, int mousex, int mousey)
{
int i, dist;

if ( root == NULL ) return; // Sub-tree is empty. This situation will generally not occur

dist = sqrt(pow((mousex - root->px),2) + pow((mousey - root->py),2));

printf("distance = %d\n", dist);

if (dist<5)
{

printf("delete this point\n");
deleteNode(root->children[i], mousex, mousey);
free(root->children[i]);
root->children[i] = NULL;

return;
}
else {
for (i=0; i<4; i++) 
{
if ( root->children[i] != NULL )
{
deleteNode(root->children[i], mousex, mousey);
}
}
}

}

[Seraphim0240]

does anyone have the slightest clue what to do next? i attached my .c file down at the bottom...

[MK27]

Okay: so have you done a quad tree before, or are you learning to do it in the context of your openGL project?

If the latter is true, start thinking about some of the reasons why that is not a good plan. For example, now you are stucking posting masses of code no one is interested in.

[tabstop]

Well, I'm not really clear what your problem is. There are two branches in your code:
(a) if dist is less than 5 you remove the node you are on and all of it's descendants
(b) if dist is 5 or more you call the function recursively on all the children.

If you don't want to delete all of the descendants, then don't do that, I guess; otherwise I'm not sure what problem you're having.

[Perspective]

In the first if block, "i" is not initialized. I'm guessing that should be in a loop.

[Seraphim0240]

Well, I'm not really clear what your problem is. There are two branches in your code:
(a) if dist is less than 5 you remove the node you are on and all of it's descendants
(b) if dist is 5 or more you call the function recursively on all the children.

If you don't want to delete all of the descendants, then don't do that, I guess; otherwise I'm not sure what problem you're having.

Yeah, I can't figure out how to not delete all of the descendants and only the current node that the user right-clicked on... That's where I'm stuck. I have no idea how to begin coding that.

And to the guy who said this isn't the best way to learn quadtrees and I shouldn't be posting code no one is interested in, you can tell that to my professor. He assigned us a project over spring break that none of us know how to do since he didn't teach us how quadtrees work and/or the syntax that goes with them... and since the university is shut down for the week, there are no tutors/teaching assistants to help us. So here I am on a computer programming forum. Thanks for your input though.

[tabstop]

Yeah, I can't figure out how to not delete all of the descendants and only the current node that the user right-clicked on... That's where I'm stuck. I have no idea how to begin coding that.

Really? You don't see the line that calls "delete" on the children? And "free" on the children? You don't know how to remove those lines?

Now, you do have the question -- where are those nodes supposed to go? You can't just leave them hanging as children of a nonexistent node -- you'll need to hook them back to the tree.

[MK27]

to the guy who said this isn't the best way to learn quadtrees and I shouldn't be posting code no one is interested in, you can tell that to my professor. He assigned us a project over spring break that none of us know how to do since he didn't teach us how quadtrees work and/or the syntax that goes with them... and since the university is shut down for the week, there are no tutors/teaching assistants to help us. So here I am on a computer programming forum. Thanks for your input though.

In other words, you are stuck having to figure out quad trees yourself. My point was, you are only making it harder on yourself by doing that within your openGL project. Your life will be much simpler and easier if you take a few deep breaths and try and write a short quad tree "demo" program for yourself, sans any other concerns.

And, chances are, the implementation you transplant (OMG: tree pun) into the GL code will probably be the better for it too.